Harmon Kardon 7 logic Sub woofer problem

[C250cgicoupe]

Hi, the sub woofer on the parcel shelf of my 2014 c204 coupe has started to rattle even when the base is set very low, this used to be an occasional problem and would play fine 9/10 times I played my stereo but is now constantly rattling/vibrating, my car was recently in at Mercedes for a gearbox service but they didn't have time to diagnose if the speaker was at fault and suggested I bring the car back and leave it with them for several day's to confirm. I'm assuming the speaker is the problem (7 logic harmon kardon) I have never really cranked my stereo very high so a bit surprised it's knackered.

Have any other members had a similar problem with their 7 logic sub woofer? The prices I've seen on the internet for a genuine replacement seem completely mad and are as much as I paid for the 7 logic option on the car when I bought it new. Also from what I can see it will involve dismantling a lot of the interior to get access to the speaker, so my question was would it be feasible to replace it with a loose sub woofer in the boot by simply disconnecting the original and connecting up the new item or is there something about the 7 logic stereo that would prevent this?

thanks for any advise.